Existing lawnmower designs can easily lead to overheating of the electrical components, as a result of high cutting loads, high ambient temperatures or a combination of both. Overheating can affect both the electronics and the batteries, particularly Lithium-ion batteries. This is particularly true for robotic lawn mowers. They will typically will be out in the sun most or all of the time especially when they are coupled to a docking station either having the batteries recharged or simply waiting for their next scheduled cutting operation. Using Lithium-ion batteries, the electronics in these devices are typically configured to prevent the product operating if the cells are above a certain limit temperature (usually 70° C.) to prevent permanent damage or, in extreme cases catching fire. There is therefore a need for additional cooling steps for these devices, particularly to prevent them from simply not operating in hot climates. Robotic devices typically have an outer shell, which is used in collision detection. This outer shell will provide some shading effect against ambient high temperatures, but will also mean that venting is required to allow air cooling of the device. Some cooling effect will be provided by the fan effect of rotating blades. However, this will be insufficient due to the low power provided to the cutting blades in such mowers. Attention also needs to be paid to the cooling of the device when it is not in operation.
Cooling fans have not been used in previous designs for battery operated robotic lawn mowers, because of the additional power requirements of the fan in operation. However, it will be shown that careful design and placement of vents in combination with a fan or impeller allow advantages in both cooling and debris removal.